function q = Geta_vec(invP,j,v)

k = 1/invP.disT(1,2);

tmp = invP.mesh.Af*diag(k*invP.tauModel)*v;
q = cell(size(j));
for ii = 1:invP.nt
    for jj = 1:invP.ntx
        if ii == 1
            q{ii}(:,jj) = sdiag(j{ii}(:,jj))*tmp;
        else
            q{ii}(:,jj) = sdiag(j{ii}(:,jj) - j{ii-1}(:,jj))*tmp;
        end
    end
end